Abstract Background Enlargement of the mitral leaflets (MLs) adaptive to mechanical stress caused by dilated left ventricle (LV) was recognized, but their changes after the stimuli withdrawn remained unexplored. Aims To observe morphological changes in the MLs along with LV reverse remodeling (LVRR) occurred after standard care. Methods Patients with recent-onset dilated cardiomyopathy (RODCM) were prospectively enrolled (n=82), as well as a group of age, sex and body surface area matched normal controls (NC) (n=50). Two-dimensional transthoracic echocardiography was performed at baseline and 6-month follow-up with special interests in the length of anterior and posterior mitral leaflet (AML and PML), mitral annular dimension (MAD) and tenting height (TH). LVRR was measured as a reduction in the LV end-diastolic volume (LVEDV) of ≥15%. Results At the 6-month follow-up, LVRR was achieved in 69.5% patients and there were 26.9% patients who reported ≥1 grade reduction in secondary mitral regurgitation that related to LVRR. The AML (28±3 vs. 26±3mm, p=0.004) and PML (19±4 vs. 17±3mm, p<0.001) were decreased, as well as the MAD (31±5 vs. 28±5mm, p=0.001) and TH (10±3 vs. 8±2mm, p<0.001), but all remained larger than that of the NC group (all p<0.05). When compared with the control group, the AML and PML of the RODCM group was 16.7% and 35.7% longer at baseline, which remained 8.3% and 21.2% longer at the follow-up, respectively. The change in the AML (△AML) or PML (△PML) correlated moderately to the change in the LVEDV (△LVEDV) (r=0.487, p<0.001; r=0.516, p <0.001, respectively) (Figure 1). When compared between the subgroups stratified by LVRR, both the AML and PML decreased in the patients who had LVRR (+) (AML, 28±3 vs. 26±3, p=0.001; PML, 20±4 vs. 16±3, p<0.001), but remained the same length in those with LVRR (-) (AML, 27±4 vs. 28±4, p=0.318; PML, 17±3 vs. 17±3, p=0.790). The comparison in the △AML and △PML between the two subgroups is shown in Figure 2. Conclusion The enlarged MLs could retract with different behavior in the AML and PML, accompanied by LV reverse remodeling. This study conducted in patients with RODCM who received standard therapy provided the other facet of mitral leaflet plasticity adaptive to mechanical stretch.correlation between △MLs and △LVEDVCompare △MLs between LVRR subgroups
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